(1) Field of the Invention
This invention relates to a filter device and, more particularly, to a filter device which is suitable for removing microaggregates from blood.
(2) Description of the Prior Art
Blood for transfusion purposes contains microaggregates which are produced during the storage of the blood. If the blood is transfused to a patient without removing the microaggregates will, they cause various adverse reactions. Also, in dialyzing blood similar problems will arise if microaggregates which have been attached to the filtering surfaces of a dialyzer are released therefrom and mixed with blood remaining in a dialysis circuit at the time when the blood is returned into the patient's body by blowing air from the inlet side of the dialyzer after the dialysis is completed.
There have been developed various blood filter devices for removing microaggregates from blood. These filter devices include those of a soft bag type capable of deformation according to the rate of flow of blood and those of a rigid type incapable of deformation. These two kinds of filters have their respective merits and demerits so that in practice they are used alternatively according to the desired end use.
Japanese Patent Application Disclosure No. 52-116969 (laid open to the public on Sept. 30, 1977 in Japan) discloses a rigid blood filter device, in which a blood inlet and a blood outlet are provided such that they are substantially aligned with each other, and which has a housing extending in a direction at right angles to a line connecting the blood inlet and outlet. A filter element is provided within the housing such that it extends in a direction at right angles to the afore-mentioned line.
Since in this filter device the housing extends in a direction crossing the line connecting the inlet and outlet, it takes much space so that inconveniences exist in its handling in clinical use. In addition, blood is brought into contact with the filter element in a direction at right angles thereto so that it chiefly passes through only a central portion of the element (that is, partial flow results). Thus, there is a deficiency that the entire surface of the filter element cannot be uniformly and effectively used.
Further, a filter element, in general, tends to be clogged if its filtering efficiency is increased under a fixed filtering area, while the filtering efficiency is lowered if mesh size is increased to prevent clogging. Therefore, it is necessary to enlarge the filtering area in order to provide a filter element having a high filtering efficiency. In this connection, if the filter element is simply enlarged in such a filter device as in Japanese Disclosure No. 52-116969, the resultant device would become large in size, presenting an inconvenience in handling.